As is well known in the art, a canister is disposed to a side of a fuel tank such that an inner pressure by a fuel gas generated in the fuel tank can be controlled. In a case that the canister or the like does not exist, the inner pressure of the tank may rise because of the fuel gas, consumption of fuel increases, and air pollution can occur as a result of gas leakage.
Typically, a filler pipe for supplying fuel to a fuel tank is connected to one side of the fuel tank. A filler neck for accommodating a gasoline pump nozzle to be being inserted therein is formed to an upper end of the filler pipe. One end of the filler neck protrudes into a fuel inlet space formed between a vehicle body and a fuel cap door such that the end of the filler neck is opened/closed by a fuel cap. In addition, the filler neck and the fuel tank are connected by a leveling pipe. The leveling pipe is typically for controlling an amount of fuel delivered to the fuel tank, depending on a pressure of the fuel supplied to the fuel tank during a fuel supplying process.
An upper portion of the fuel tank and a canister are connected with each other by a fuel evaporation gas line. The fuel evaporation gas generated in the fuel tank flows into the canister through the fuel evaporation gas line. The fuel evaporation gas flows into the canister in a state where an engine stops is captured by activated carbon in the canister. A fuel element in the canister is purged into an intake system of the engine through the purge line by an opening operation of a purge control valve when the engine is operating.
An end of an air passage is connected to the canister such that the purge operation is more easily done in the canister and another end of the air passage is connected to an air filter located to one side of the filler neck. The air filter is intended to eliminate foreign substances mixed in the air supplied to the canister.
On the other hand, the air passage and the air filter are also utilized as passages such that an inner pressure of the canister is lowered during a situation where the inner pressure of the fuel tank and the canister is excessively high. However, when a vehicle, having the fuel system as described above, drives in poor road conditions, such as on an unpaved road, the air filter can become plugged because foreign substances, such as dust or dirt, can accumulate in the air filter.
Also, if the fuel evaporation gas is purged when the air filter is plugged by foreign substances, a pressure developed in the intake system can excessively affect the canister and the fuel tank, thereby potentially causing deformation or cracks of the fuel tank.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention, and therefore, unless explicitly described to the contrary, it should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.